I. Background of the Invention
This invention relates to heat exchanged hydrogen membrane reactors. More particularly, the invention relates to a hydrogen membrane reactor that employs catalytic or stream reforming and a water gas shift reaction on one side of the membrane, and hydrogen combustion on the other side of the membrane. A portion of the heat of the highly exothermic hydrogen combustion is exchanged through the membrane to supply heat to the reforming reaction. The hydrogen combustion product is used to power a turbine for producing electricity.
II. Description of the Related Art
Steam reforming to produce elemental hydrogen is generally known in the art. An idealized steam reforming reaction for a methane feed is represented by the equation:
CH4+H2Oxe2x86x923H2+CO
The above-described reforming reaction is highly endothermic, having a heat of reaction of approximately 88,630 BTU/Mole. Reforming reactions of other hydrocarbon feeds are similarly endothermic. Water Gas Shift reactions to produce hydrogen from carbon are also generally known in the art. An idealized water gas shift reaction for a CO feed is represented by the equation:
xe2x80x83CO+H2Oxe2x86x92H2+CO2
This is a mildly exothermic reaction, having a heat of reaction of approximately xe2x88x9217,698 BTU/Mole.
Hydrogen permeable membranes are also generally known in the art, and have been utilized in hydrogen separation in varied applications. The present invention however, utilizes a hydrogen membrane in a novel reactor configuration that is particularly adapted to combust the hydrogen and use its heat of combustion in the hydrogen producing reaction while using the energy of combustion to power or turbine.
The present invention is directed to a heat exchanged membrane reactor that (A) separates hydrogen from a hydrocarbon source using a membrane, (B) combusts the hydrogen, (C) transmits a portion of the heat of the combusted hydrogen to an endothermic reformer process, (D) uses the product of the hydrogen combustion to power a turbine for power generation. The heat exchanged membrane reactor employs thermal or catalytic steam reforming of a hydrocarbon feed to produce hydrogen, which permeates the reactor membrane to the opposite side, where it is combusted. A portion of the heat of combustion is transmitted through the membrane to supply heat to the reforming reaction, a highly endothermic reaction. The combustion product is used to power a turbine for generating electricity. In a further embodiment, a water gas shift reaction is employed on the reformer side of the membrane reactor to convert CO to CO2 that may be conveniently sequestered. The heat-exchanged membrane need withstand elevated temperatures, ranging from about 400xc2x0 C. to about 1400xc2x0 C., and have hydrogen permeance of at least a portion of the membrane ranging from about 1 Mole/(Meter2-Day-Atmosphere of H2) to about 106 Moles/(Meter2-day-atmosphere of H2). In a preferred embodiment, the reforming reaction and at least a portion of the hydrogen combustion occurs proximate to the membrane to facilitate the heat transfer.